Elongated CO Structure in the Starburst Galaxy NGC 2146

Aperture synthesis observations of the CO J = 1-0 line from the starburst galaxy NGC 2146 were obtained with the Hat Creek Millimeter Interferometer. The spatial resolution is 6" in a 2' field of view; the spectral resolution is 52 km s^-1^. Warm (>~10 K) CO is detected in an elongated structure ~3.0 x 0.7 kpc at position angle 134^deg^, coincident with radio continuum emission but not coincident with the prominent optical dust lane. This CO structure may be a bar or a disk viewed edge-on. A velocity gradient of 0.2 km s^-1^ pc^-1^ is measured along this structure, about twice the gradient measured from optical lines. This gradient is probably due to rotational motions and suggests that the molecular material is closer to the nucleus than the optically emitting gas. There is no evidence for highly disturbed motions. If a merger is important for this system, the molecular gas shows no evidence for noncircular motions, suggesting that it has had sufficient time since the merger to relax. On size scales of a few hundred parsecs, the CO and radio synchrotron emission have very similar distributions. The extensive nature of the high-temperature gas may be a signpost of intense nuclear activity. The L_IR_/L_CO_ ratio in NGC 2146 is similar to that in M82, but the luminosities and size scale of the starburst region are larger. We suggest that the starburst in NGC 2146 is a scaled-up version of M82.